This invention relates to a technique for treating polytetrafluoroethylene. More particularly, the present invention relates to a technique for etching the surface of polymeric tetrafluoroethylene. The invention also relates to a technique for enhancing the adherency of polytetrafluoroethylene surfaces.
During the past decade, there has been a dramatic increase in the industrial use of polytetrafluoroethylene, so creating a need for the development of novel processing techniques for both its preparation and subsequent use. Prior to applicants' entry into the field, workers in the art recognized that tetrafluoroethylene polymers could be effectively etched or attacked by molten alkaline metals, gaseous fluorine at elevated temperatures or by means of a solution comprising sodium in anhydrous ammonia (See, for example, Brockhaus ABC Chemie, Brockhaus Verlag, Leipzig 1965, Page 1119). Unfortunately, although these techniques were theoretically efficacious, serious impediments essentially precluded their use. Thus, for example, the use of molten alkaline metals in conjunction with polytetrafluoroethylene results in an explosive mixture whereas the use of gaseous fluorine presents inherent toxicity problems. Although liquid (anhydrous) ammonia does not suffer from these deficiencies, its use is practical only at reduced temperatures and elevated pressure. Accordingly, a need has long existed for a commercially feasible alternative for modifying the surface of polytetrafluoroethylene.